The present invention relates to hydrocarbon production treatments. More particularly, the present invention relates to methods and compositions for delaying the release of treatment chemicals. Even more particularly, the present invention is directed toward encaged treatment chemicals and methods of using them in subterranean applications. The term “encaged treatment chemical” refers to a “treatment chemical” that is encaged within a three-dimensional “polymer carrier” so that its release may be delayed.
In hydrocarbon exploration and production, a variety of treatment chemicals may be used to facilitate the production of the hydrocarbons. These include gel breakers, dispersing agents, and defoamers, among others. Unfortunately, many treatment chemicals may be adversely affected by exposure to the well bore environment before the chemicals reach their desired destinations in the subterranean formation. This can result in the reaction of the treatment chemical within the well bore, which, depending on the treatment chemical, could affect negatively the production potential of the well. The functionality of a particular fluid system may be adversely affected if a treatment chemical is released prematurely.
To combat these potential production setbacks, a variety of chemical or mechanical methods have been used to inhibit the interaction of the treatment chemical with the well bore environment. Some methods involve physically isolating the treatment chemicals from the well bore environment by injecting the chemicals into the reservoir through coiled tubing or a similar material. Other methods have used porous media to absorb the treatment chemical and then allow it to diffuse out of the media over time. Still other methods have encapsulated the treatment chemical within a degradable coating that degrades down hole to release the treatment chemical at a desired time or place. Several problems exist with conventional encapsulation techniques. For instance, in applications using latexes, rubbers, plastics, or zeolite materials to coat or encapsulate a treatment chemical, inadequate control over the size of pore throats and/or the surface areas of exposed surfaces has prevented consistent, reliable applications. FIG. 1A is an illustration of an encapsulated treatment chemical for a comparative illustration. Shown at 100 is a treatment chemical that is coated by coating 102. FIG. 1B illustrates some of the problems that can exist with encapsulated treatment chemicals. For example, coating 102 has imperfections 104. Also, treatment chemical 100 is not completed coated with coating 102, and therefore, may not be protected from diffusion to the extent necessary to achieve the desired purpose.
Another conventional method that has been suggested to delay the release of a treatment chemical involves the use of “clathrates,” which is a unique class of chemical compounds in which a rigid, open network of bonded host molecules enclose, without directly chemically bonding to, appropriately-sized guest molecules of another substance. However, development clathrate-based treatment chemicals has been problematic. For example, the release rate is typically such that the treatment chemical is released too slowly to be used as an effective delivery mechanism, if the chemical is released at all. Thus, unable to reliably release the treatment chemical, clathrate-based delivery mechanisms have proven inadequate for hydrocarbon production treatments to date.